Two experiments were conducted to enhance the corpus luteum (CL) function for increasing lambing rate of ewes treated with GnRH or hCG after artificial insemination (AI) during the non-breeding season. Ewes (Experiment 1: n=102, Experiment 2: n=37) were pretreated with a controlled internal drug release dispenser (CIDR) for 12 days and 500 IU equine chorionic gonadotropin (eCG) 1 day before CIDR removal. In Experiment 1, the ewes were treated on Day 12 (Day 0=CIDR removal): 1) Group I; GnRH (100 μg), 2) Group II; hCG (500 IU), 3) Group III; 0.6% saline (2 ml) for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups. But, there was significant (P<0.01) difference in the lambing rate between parous (27%) and non-parous (72%) in Group I. On Day 17, plasma progesterone (P₄) levels of Group I were significantly (P<0.01) lower than those of Group III, but on the contrary, the plasma P₄ levels of Group II were significantly (P<0.01) higher than those of Group III. In Experiment 2, the ewes were treated: 1) Group I; hCG (500 IU) on Day 6, 2) Group II; hCG (500 IU) on Day 9, 3) Group III; no treatment for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups, but on Days 12 and 15, the plasma P₄ levels of Groups I and II were significantly (P<0.01) higher than those of Group III. The present results indicate that a single hCG treatment on Days 6, 9 and 12 after CIDR removal stimulates CL and increased P₄ concentration, but the increased P₄ levels did not reflect on the fertility of treated ewes.